Synthesis, structure and catalytic activity of low-spin dicyano iron(III) complexes of N,N′-bis(quinolyl)malonamide derivatives

Article abstract of DOI:10.1016/j.ica.2004.01.019

Two low-spin Fe(III) dicyano-dicarboxamido complexes have been prepared from N,N^′-bis(8-quinolyl)malonamide derivatives. Crystal structures show that the four nitrogen donors available to complex the metal are arranged in the equatorial plane w

Full text of DOI:10.1016/j.ica.2004.01.019

Inorganica Chimica Acta 357 (2004) 2211–2217
www.elsevier.com/locate/ica
Synthesis, structure and catalytic activity of low-spin
dicyano iron(III) complexes of N; N0-bis(quinolyl)malonamide
derivatives q
a
Olaf Rotthaus , Sophie Le Roy , Alain Tomas , Kathleen M. Barkigia ,
a
b
c
a,
*
Isabelle Artaud
a
Laboratoire de Chimie et Biochimie Toxicologiques et Pharmacologiques, Universitꢀe Renꢀe Descartes, Univ Paris 5, UMR8601,
45 rue des Sts Pꢁeres, 75270 Paris cedex 06, France
b
Laboratoire de Cristallographie et de RMN biologiques, Facultꢀe de Pharmacie, UMR 8015, 4 rue de lÕObservatoire, 75270 Paris cedex 06, France
Department of Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
c
Received 5 June 2003; accepted 18 January 2004
Available online 26 February 2004
Abstract
Two low-spin Fe(III) dicyano-dicarboxamido complexes have been prepared from N; N0-bis(8-quinolyl)malonamide derivatives.
Crystal structures show that the four nitrogen donors available to complex the metal are arranged in the equatorial plane with the
two cyanides trans to each other in the axial positions when the malonyl moiety is disubstituted. In contrast, the unsubstituted
malonyl results in only three nitrogens in the equatorial plane with the fourth in an apical position and the two cyanides occupying
cis sites, one equatorial and the other axial. NMR analyses show that the solid state structure of both complexes is retained in
solution. Both types of configurational complexes catalyze cyclic olefin oxidations with H2O2 but only the cis-dicyano complex
catalyzes stilbene oxidation with formation of epoxides, diols and benzaldehyde.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: N; N0-bis(8-quinolyl)malonamide; Iron(III) complex; Oxidation; Stilbene
1. Introduction
3d,4,5]. Complexes containing dianionic bis(amidate) li-
gands, usually derived from picolinic acid, afford six-co-
ordinate complexes with an equatorial N4 core and two
apical exogenous ligands [3c,4,6,7]. We report here the
syntheses, structures and reactivities of new dicyano
Fe(III) complexes derived from N; N0-8-quinolylmalo-
namide derivatives (Fig. 1). The spatial configuration of
the bis-carboxamido ligands depends on whether the
methylene position of the malonamide is unsubstituted or
disubstituted, yielding six-coordinate complexes with two
cis or trans cyanides which exhibit different oxidative
activity with H2O2 toward cyclic olefins and stilbene.
There has been growing interest in developing mimics
of mononuclear non-heme iron proteins capable of cat-
alyzing alkane hydroxylation [1], olefin epoxidation, and
more recently, olefin cis-dihydroxylation [2]. Most of the
complexes reported so far which catalyze cis diols for-
mation contain amine and pyridine nitrogen donors, such
as tris-(pyridylmethyl)amine ligands, which stabilize the
Fe(II) state [2]. Introduction of one or more carboxamido
nitrogens in the coordination sphere is known to increase
the stability of Fe(III) [3a] and affords mononuclear
Fe(III) complexes which exhibit significant oxidative ac-
tivity with peroxides such as H2O2 or tBuOOH [3b–
2. Experimental
2.1. Physical measurements
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2004.01.019.
* Corresponding author. Tel.: +33142862189; fax: +33142868387.
E-mail address: isabelle.artaud@univ-paris5.fr (I. Artaud).
UV–Vis spectra were recorded on a Safas UV mc2
spectrophotometer. X-band EPR spectrum was
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.01.019

2212
O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
lonic ester was carried out by the procedure reported by
Maslak et al. [9].
2.3. Synthesis of complexes 2a and 2b
In a typical experiment, performed under argon, 100
mg FeCl2 ꢁ 4H2O (0.5 mmol, 1 equiv) was dissolved in 5
mL DMF and combined with 1 equiv of the corre-
sponding ligand in 20 mL DMF. Upon addition of
200 lL NEt3 (3 equiv), the solution turned dark red. The
mixture was cooled to )30 °C and 0.47 g Et4NCN (6
equiv) in 10 mL DMF was added (color turned into
intense green), followed by 200 mg of the oxidizing
agent C6H4FN2PF6 [10] (1.5 equiv) in 5 ml DMF. The
final dark brown solution was allowed to warm to r.t.
and the solvent was removed in vacuum. The crude
product was dissolved in 25 mL MeOH and the re-
maining white residue (unconverted ligand) was filtered
off before the green complex was precipitated by addi-
tion of ether. (2a: 265 mg, 2b: 347 mg, yield 2a, 2b: 90%).
The complexes were further additionally purified over a
Sephadex LH-20 resin (Amersham Biosciences).
Analytical data and spectroscopic properties of the
complexes: [Fe(BQM)(CN)2]Et4N (2a): Anal. Calc. for
C34H50N7O7Fe (2a ꢁ 2H2O ꢁ 3CH3OH): C, 56.53; H,
6.95; N, 13.53. Found: C, 56.04; H, 6.94; N, 13.44%. 1H
NMR (CD2Cl2, ppm): 17.7, 11.9, 10.4, 9.2, 7.0, 5.0, 1.2,
)2.8, )7.3, )11.6, )20.8, )25.3, )29.5 (1H each). Se-
lected IR frequencies (KBr, cmꢀ1): 2116 (w, mCN), 1616
(m, mCO). Electronic absorption kmax nm (e, Mꢀ1 cmꢀ1):
CH2Cl2, 250 (2.0 ꢂ 104), 368 (3.2 ꢂ 103), 440 (2.5 ꢂ 103),
696 (7.1 ꢂ 102). EPR (DMF, 5% H2O): gx ¼ 2:52,
gy ¼ 2:19, gz ¼ 1:82. E1=2[Fe(BQM)(CN)2]2ꢀ=ꢀ(versus
SCE) (DMF, Bu4NBF4, 10 equiv Et4NCN, 20 °C): )605
mV (DE ¼ 90 mV). [Fe(BenzBQM)(CN)2]Et4N (2b):
Anal. Calc. for C47H49N8O2Fe (2b ꢁ CH3CN): C, 69.37;
H, 6.07; N, 13.77. Found: C, 68.92; H, 6.07; N, 13.76%.
1H NMR (DMSO-d6, ppm): 10.4 (2H), 7.5–6.9 (10H,
ar), 5.4 (2H), 1.3 (2H), )0.5 (4H, CH2), )8.2 (2H), )13
(2H), )26.5 (2H). Selected IR frequencies (KBr, cmꢀ1):
2112 ðw; mCNÞ, 1607 ðm; mCOÞ. Electronic absorption kmax
nm (e, Mꢀ1 cmꢀ1): MeOH, 254 (2.7 ꢂ 104), 362
(4.2 ꢂ 103), 440 (5.0 ꢂ 103), 702 (9.3 ꢂ 102). EPR (DMF,
5% H2O): gx ¼ 2:56, gy ¼ 2:15, gz ¼ 1:82. E1=2[Fe(Ben-
zBQM)(CN)2]2ꢀ=ꢀ(versus SCE) (DMF, Bu4NBF4, 10
equiv Et4NCN, 20 °C): )645 mV (DE ¼ 110 mV).
Fig. 1. Ligands.
recorded on an ALEXIS spectrometer operating at a
9.45 GHz microwave frequency (100 kHz modulation
frequency, 1 mT modulation amplitude, 20 mW micro-
1
wave power). H NMR spectra were recorded at 300 K
on a Bruker ARX-250 spectrometer. Chemical shifts are
reported in ppm downfield from TMS. Infrared spectra
were obtained as KBr pellets or directly from the solid
compounds (neat) with a Perkin–Elmer Spectrum One
FT-IR spectrometer. Cyclic voltammetry experiments
were performed with a potentiostat Radiometer PJT-1
controlled by an interface Radiometer IMT-1 using so-
lutions containing 0.1 M Bu4NBF4 as supporting elec-
trolyte. The three electrode systems consisted of an
NaCl saturated calomel electrode (SCE) as reference, a
platinum auxiliary electrode and a glassy carbon work-
ing electrode. Ferrocene was used as an internal stan-
dard (E1=2(Fc0=þ) in DMF, 50 mV/s, +508 mV at 20 °C
and +515 mV at )40 °C). Elemental analyses were
carried out by the microanalysis service at Paris VI
University.
2.2. Synthesis of the ligands
N; N0-Bis(8-quinolyl)malonamide BQMH2: under
argon malonyl chloride (972 lL, 9.5 mmol) was added
to a solution of 8-aminoquinoline (3.17 g, 22 mmol) and
triethyl amine (1.5 mL,10 mmol) in 100 mL of CH2Cl2.
After addition of another 1.5 mL triethyl amine, the
mixture was stirred for 12 h. CH2Cl2 was added until all
precipitated condensation products were dissolved, then
the solution was washed three times with water and then
with saturated NaHCO3. After drying over Na2SO4, the
solvent was removed and the product was recrystallized
from CH2Cl2 (m ¼ 1:32 g, yield 39%). Anal. Calc. for
C21H16N4O2: C, 70.78; H, 4.49; N, 15.73. Found: C,
70.60; H, 4.66; N, 15.68%. 1H NMR (CDCl3, ppm):
10.78 (s, 2H, NH), 8.89 (dd, J ¼ 1:6, 4.4 Hz, 2H), 8.83
(dd, J ¼ 3:6, 5.6 Hz, 2H), 8.16 (dd, J ¼ 1:6, 8.4 Hz, 2H),
7.55 (dd, J ¼ 3:6, 5.6 Hz, 2H), 7.46 (dd, J ¼ 4:4, 8.4 Hz,
2H), 3.87 (s, 2H). IR (neat, cmꢀ1): 3279 ðw; mNHÞ, 1646
ðm; mCOÞ.
2.4. X-ray crystallography
Crystal data and data collection parameters for
complexes 2a and 2b are summarized in Table 1, while
selected bond angles and distances are listed in Table 2.
2.4.1. X-ray crystallography of 2a
Data were measured at 108 K on a MAR345 image
plate detector at beamline X7B at the Brookhaven
The substituted ligand 1b was synthesized according
to Hirose et al. [8b], but the saponification of the ma-

O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
2213
Table 1
Crystal data and structure refinement
suite programs was used to treat this problem [14]. The
residual density in the final difference Fourier does not
ꢂꢀ3
Formula
C
31H34N7O2Fe,
C47H49N8O2Fe (2b)
show any feature above 0.635 e A and below )0.343 e
2(H2O) (2a)
methylene chloride/
toluene
ꢂꢀ3
A
.
Crystallized from
acetonitrile/
diethylether
813.79
2.4.2. X-ray crystallography of 2b
Formula weight
Space group
Z
628.53
C2=c
8
108
Intensity data were collected on a Xcalibur system
using x-scan technique (Dx ¼ 1°, 460 frames, the ex-
posure time depending on the intensity of the frame)
[15]. The structure was solved by direct methods using
SHELXS-97 [16] and refined by full matrix least-squares
methods on F2 [17]. Non-hydrogen atoms were refined
with anisotropical thermal parameters. Hydrogen atoms
were calculated for idealized geometries and refined as
riding models with isotropic parameters constrained to
be 1.2 times the Ueq of the carrier atom. The residual
density in the final difference Fourier does not show any
Pbc21
4
180
T (K)
ꢂ
a (A)
33.778 (8)
13.747 (1)
14.288 (4)
90
11.114 (1)
19.172 (3)
19.384 (3)
90
ꢂ
b (A)
ꢂ
c (A)
a (°)
b (°)
c (°)
92.69 (1)
90
90
90
3
ꢂ
Volume (A )
Crystal color
Crystal shape
Density calculated
(g/cm3)
6627.3 (2)
dark blue
irregular cube
1.260
4130.8 (8)
dark green
parallelepiped
1.309
ꢂꢀ3
ꢂꢀ3
feature above 0.473 e A and below )0.439 e A
ORTEPII was used to produce molecular graphics [18].
.
Dimensions (mm)
/ (mmꢀ1
0.08 ꢂ 0.07 ꢂ 0.07
0.499
0.9376
0.10 ꢂ 0.28 ꢂ 0.08
0.415
0.71073
)
ꢂ
k (A)
2.5. Catalytic oxidation reactions
2h range (°)
Reflections
2.11–30.94
45 433/4065
3.67–30.32
35 189/11 499
measured/unique
Reflections with
I > 2rðIÞ
Oxidation reactions with complexes 2a and 2b were
carried out in the presence of air under atmospheric
pressure. For cyclooctene and cyclohexene, the complex
(1 lmol) and the substrate (800 lmol) were dissolved in
1 mL acetonitrile and the mixture was stirred at 65 °C.
Stepwise addition of H2O2 was performed as mentioned
3774
389
8180
528
Number of
parameter refined
R1; wR2 ðI > 2rðIÞÞ
R1; wR2 (all data)
Goodness-of-fit
0.051; 0.148
0.057; 0.163
1.096
0.049; 0.086
0.077; 0.0956
0.942
Table 3
Results of olefins oxidation with complexes 2a and 2b in acetonitrile at
65 °C
Table 2
ꢂ
Substrate/productsa
Equivalents of products relative to
complex
Selected bond angles (°) and distances (A) for complexes
[Fe(BQM)(CN)2]Et4N (2a) and [Fe(BenzBQM)(CN)2]Et4N (2b)
2a
2b
Fe(BQM)(CN)2 Fe(BenzBQM)(CN)2
(2a)
(2b)
Fe–N1
Fe–N2
1.974(3)
1.958(2)
1.940(3)
2.032 (3)
1.954(4)
1.930(4)
1.152(4)
1.147(4)
100.89(10)
90.05(12)
83.71(13)
171.88(12)
168.97(12)
1.982(2)
1.916(2)
1.941(2)
2.000(3)
1.968(3)
1.975(3)
1.152(3)
1.145(3)
173,77(9)
100.54(8)
171.79(9)
95.25(10)
84.64(9)
Cycloocteneb;c
Cyclooctene oxide
Cyclooctene diol
40 (19)d
6 (2)d
42 (22)d
7 (2)d
Fe–N3
Fe–N4
Fe–C22
Fe–C23
Cyclohexenec;e
Cyclohexene oxide
2-cyclohexene-1-ol
2-cyclohexene-1-one
9
7
C22–N5
C23–N6
39
41
37
38
N2–Fe–N4
N1–Fe–N4
C23–Fe–C22
C22–Fe–N2
C23–Fe–N4
cis-stilbenef ;g
cis-stilbene oxide
trans-stilbene oxide
cis-silbene diol
trans-stilbene diol
Benzaldehyde
0.5
4.3
1.3
0.9
16.0
0.1
0.1
0.1
not detected
1.9
a Products were identified by comparison with authentic samples.
b Addition of 5 ꢂ 60 equiv H2O2 in intervals of 1 h.
National Synchrotron Light Source. The data were
scaled and merged using Denzo/Scalepack [11]. The
structure was solved with SIR92 [12] and refined on F2
c Yields were determined after 8 h by gas chromatography.
d Values in brackets were obtained with 0.5 equiv of catalyst.
e Addition of 12 ꢂ 25 equiv H2O2 every 30 min.
(
SHELXTL Version 5) [13]. The lattice contains an ex-
f Addition of 8 ꢂ 20 equiv H2O2 every 30 min.
g Yields were determined after 5 h by NMR integration of charac-
teristic protons. Reactions were carried out in acetonitrile-d3.
tremely disordered molecule of solvation, which was
unmodelable. The program SQUEEZE in the PLATON

2214
O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
in Table 3. After 8 h, 20 equiv of acetophenone were
added as an internal standard and the amounts of oxi-
dation products were determined by G.C. For stilbene, 1
mL of acetonitrile-d3 was used as a solvent and (due to
the reduced solubility) 0.5 lmol of catalyst was em-
ployed with 200 equiv of the substrate. After 5 h,
product yields were determined by NMR integration of
characteristic protons compared to the methyl group of
acetophenone (standard). All reactions were run at least
in triplicate and the reported data represent the average
values.
3. Results and discussion
N; N0-Bis(8-quinolyl)malonamide, 1a, was readily
synthesized by condensing 8-aminoquinoline with mal-
onyl dichloride. The disubstituted derivative 1b, which
has been previously reported and shown to complex
divalent metals [8], was synthesized as described in
[8b,9]. Fe(II) was readily incorporated into all two li-
gands with FeCl2 ꢁ 4H2O in the presence of the soft base
Et3N. Addition of Et4NCN, followed by oxidation of
the resulting dicyano iron(II) complexes with the one-
electron oxidizing agent 4-fluorobenzenediazonium
hexafluorophosphate [10], afforded in good yields the
two iron(III) complexes [Fe(BQM)(CN)2]Et4N, 2a
and [Fe(BenzBQM)(CN)2]Et4N, 2b. The structures of
complexes 2a and 2b have been determined by X-ray
crystallography.
Figs. 2 and 3 show the structures of 2a and 2b, re-
spectively, and selected bond angles and distances are
listed in Table 2. The two structures reveal an octahedral
environment for the Fe(III) centers. However, while the
four nitrogen donors N1–N4 in 2b lie in the equatorial
plane with the two cyanides situated axially and trans to
each other (Fig. 3), in 2a only three nitrogens, N1, N2,
N3, lie in the equatorial plane with the fourth, N4, in an
Fig. 3. Thermal ellipsoid plot (50% probability level) of the anion of
2b. H atoms are omitted for clarity.
apical position with the two cyanides occupying cis sites,
one equatorial (C22–N5) and the other axial (C23–N6),
see Fig. 2. The steric constraints imposed by the intro-
duction of two substituents at C11 of the malonyl
fragment in 2b thus favor its planar configuration and
the resulting equatorial arrangement of all four donor
nitrogens. Note that the distances from the Fe to the
ꢂ
cyanides are essentially equivalent in 2b, 1.972(3) A, but
ꢂ
are shorter and inequivalent in 2a, 1.954(4) A and
ꢂ
1.930(4) A, reflecting the stronger donor character of the
amidate N2 relative to that of the pyridine N4.
Both complexes have been characterized in solution.
They are reversibly reduced in DMF at 20 °C, in the
presence of an excess of Et4NCN (E1=2 )605 and )645
mV versus SCE for 2a and 2b (Fig. 4(a)), respectively).
Without added cyanide as shown in Fig. 4(b), the re-
duction of the trans complex at )700 mV is followed by
two reoxidation waves at )590 and )100 mV typical of
an ECE mechanism in which one or both cyanides are
lost. The loss of cyanide(s) after the reduction thus re-
flects a low binding affinity of cyanide for the Fe(II)
state. The wave at )100 mV may be attributed to the
one-electron oxidation of a [Fe(BenzBQM)(DMF)2]2ꢀ
species having two loosely bound DMF molecules.
However, the binding affinity of cyanide to the iron(II)
increases as the temperature decreases. The reduction
became completely reversible at )40 °C and the second
oxidation wave disappeared. The same result was ob-
tained with the cis complex (data not shown). The X-
band EPR spectra of the Fe(III) dicyano in frozen
DMF/H2O 5% solution at 10 K are typical of a low-spin
iron(III) state and display a rhombic signal with g values
similar to those reported for the dicyano picolinic de-
rivatives [6,7c]. Their NMR spectra shown in Fig. 5
spread over the range )30 to +20 ppm, but are very
different as expected if their solid state structures are
Fig. 2. Thermal ellipsoid plot (50% probability level) of the anion of
2a. H atoms are omitted for clarity.

O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
2215
Fig. 5. NMR spectra of cis-2a (CH2Cl2-d2) and trans-2b (DMSO-d6) at
250 MHz.
well as comparable mCN stretching frequencies, 2116 and
2112 cmꢀ1 for 2a and 2b, respectively. Moreover, the IR
spectrum of the cis complex shows only one mCN
stretching frequency. A similar observation has been
reported for other cis-dicyano complexes such as cis-
dicyano-bis(1,10-phenanthroline)iron(II) [19] and cis-
dicyano-bis(2,2Õ-bipyridine)iron(III) perchlorate [20].
When comparing the structures of 2a and 2b, both C–N
bond distances in the two complexes fall effectively
Fig. 4. Cyclic voltammetry of trans-2b (DMF/Bu4NBF4): (a) with
Et4NCN in excess; (b) at different temperatures from 20 to )40 °C.
ꢂ
within a narrow range of 1.145 (3) to 1.152 (3) A (Table
2). This could explain the similar mCN values for 2a and
2b and the presence of only one cyanide vibration for 2a.
In contrast the Fe–CN bond lengths are significantly
retained in solution. The spectrum of 2b (Fig. 5(b))
shows six resonances, with an integration ratio of 2H
each, assigned to the 12 quinolyl protons showing that
the two quinolyl rings are equivalent. These resonances
are calibrated in reference to the signal attributed to the
four benzylic protons. In contrast, the spectrum of 2a
(Fig. 5(a)) displays 13 signals with an integration ratio
of 1H each. This result supports the absence of any
symmetry in the solution structure of 2a as in the solid
state and consequently that the two quinolyl rings are
unequivalent. Indeed, 14 resonances were expected,
since the two malonyl protons are also unequivalent,
however only 13 resonances were observed. The last
one, which is missing, is probably located under the
signals attributed to the Et4Nþ counter cation.
ꢂ
shorter in 2a than in 2b (D(2a–2b, Fe–C22) ¼ )0.014 A
ꢂ
and D(2a–2b, Fe–C23) ¼ )0.045 A, Table 2). This
should only induce differences in the lower-frequency
bands (mFeꢀCN) in the region 600–350 cmꢀ1 that we
cannot explore with a sufficient accuracy under our IR
spectrum recording conditions. The mCN of cyano com-
plexes is known to be governed by (1) the electronega-
tivity, (2) the oxidation state of the metal and (3) the
number of cyanide ligands [21]. Despite their different
structures, the properties of 2a and 2b in solution are
very similar, except for the NMR. The electronic prop-
erties of the metal center are identical in 2a and 2b in
agreement with the very similar redox potentials of these
complexes determined by electrochemistry. Their EPR
spectra display very similar g values, which are also
Despite their different configurations, the two com-
plexes exhibit similar UV–Vis spectra (see Section 2) as

2216
O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
within the range of those obtained for other dicyano
complexes containing bis-amidate ligands derived from
picolinic acids [6,7a]. CNꢀ acts as a strong r donor and
a poor p acceptor and so is not very sensitive to metal-
ligand back donation, which should be different whether
the N4 macrocycle adopts a helical or planar configu-
ration. It seems very likely that the strong effect of the
two cyanides prevails over the effect of the N4 ligand,
and therefore the electronic properties are not very
sensitive to the difference of configuration between 2a
and 2b.
dehydes, alcohols and diols with only the cis dicyano
derivative capable of selectively oxidizing the aromatic
stilbene. While the catalytic reaction is significant, these
catalysts are only poorly active. To facilitate the reac-
tion of these complexes with the oxidant, we first intend
to replace the cyanides by more labile exogenous li-
gands. This should allow: (i) to work at room temper-
ature, (ii) to limit the side reaction of H2O2
disproportionation, and (iii) to increase the difference in
the physicochemical properties according to the config-
uration of the complexes. Furthermore, the electronic
properties of the macrocycle will be modified by intro-
ducing substituents on the quinolyl ring. These modifi-
cations should allow mechanistic investigations for
understanding the different chemical reactivities of the
cis and trans complexes toward substrates.
The different structures of the two related Fe(III)
complexes with two cis or trans exogenous ligands
prompted us to test the reactivity of 2a and 2b toward
olefin oxidation in CH3CN with H2O2 as an oxidant.
Recently, it has been pointed out that the main struc-
tural feature responsible for cis-dihydroxylation of
olefins versus epoxidation was the presence of two la-
bile cis sites [2a]. Cyanide is usually proposed to be
tightly bound to the metal center, but while complexes
2a and 2b were poorly active at room temperature,
they display a significant reactivity at 65 °C. Increasing
the temperature probably allows the exchange of one
or two cyanides with the solvent and the further
binding of H2O2. The best conditions for the catalytic
oxidations were the stepwise addition of the oxidant
over time, which limited the disproportionation of
H2O2. As shown in Table 3, both complexes exhibit a
similar reactivity toward cyclooctene and cyclohexene
and favor the formation of cyclooctene oxides versus
diols (ratio ꢃ6:1), and mainly allylic oxidation of cy-
clohexene. No conversion was observed in the absence
of the catalysts. Reducing the catalyst concentration
produced a similar decrease of the conversion yields of
cyclooctene oxidation products (Table 3 and footnote
d). In contrast, while 2b was quite inactive toward
stilbene oxidation, 2a was able to convert 23 (ꢄ 2)
equivalents of the substrate (relative to the catalyst).
Besides the formation of benzaldehyde, 2a promotes
the formation of both stilbene oxides (cis:trans isomers
1:9) and diols in a 7:3 ratio. (The stilbene oxides were
stable under the experimental conditions.) Interest-
ingly, a similar product distribution has been previ-
ously described by Meunier and co-worker for stilbene
oxidation mediated by iron-bleomycin and KHSO5
[22].
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC No. 182345 for compound [Fe(Ben-
zBQM)(CN)2]Et4N and CCDC No. 211027 for com-
pound [Fe(BQM)(CN)2]Et4N. Copies of these
informations can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK [Fax: (internat.) +44-1223/336-033; e-mail: de-
posit@ccdc.cam.ac.uk, or http://ccdc.cam.ac.uk].
Acknowledgements
This work was supported by the European Com-
mission, TMR-NOHEMIP research network No.
ERBFMRXCT98-0174 and by the Division of Chemical
Sciences, US Department of Energy, under contract no.
DE-AC02-98CH10886 (at BNL). We thank the EC for
providing O.R. with a postdoctoral fellowship and
J. Fajer, J.F. Bartoli and Y. Frapart for their helpful
assistance.
References
[1] (a) M. Costas, K. Chen, L. Que Jr., Coord. Chem. Rev. 200–202
(2000) 517;
4. Conclusion
ꢀ
(b) N. Raffard, V. Balland, J. Simaan, S. Letard, M. Nierlich, K.
Miki, F. Banse, E. Anxolabehere-Mallart, J.J. Girerd, C.R. Acad.
ꢀ ꢁ
The compounds described thus represent a new class
of complexes with the same type of nitrogen donors,
whose coordination geometry to the metal center is de-
fined by a substitution on the ligand framework. As
catalysts, they yield a spectrum of olefin oxidation
products with H2O2 that include epoxides, ketones, al-
Sci. 5 (2002) 99.
[2] (a) K. Chen, M. Costas, J. Kim, A.K. Tipton, L. Que Jr., J. Am.
Chem. Soc. 124 (2002) 3026;
(b) G. Roelfes, V. Vrajamasu, K. Chen, R.Y.N. Ho, J.U. Rohde,
C. Zondervan, R.M. La Crois, E.P. Schudde, M. Lutz, A.L. Spek,
€
R. Hage, B. Feringa, E. Munck, L. Que Jr., Inorg. Chem. 42
(2003) 2639.

O. Rotthaus et al. / Inorganica Chimica Acta 357 (2004) 2211–2217
2217
[3] (a) D.S. Marlin, P.K. Mascharak, Chem. Soc. Rev. 29 (2000) 69;
(b) J.M. Rowland, M. Olmstead, P.K. Mascharak, Inorg. Chem.
40 (2001) 2810;
[9] P. Maslak, S. Varadarajan, J.D. Burkey, J. Org. Chem. 64 (1999)
8201.
[10] N.G. Connelly, W.E. Geiger, Chem. Rev. 96 (1996) 877.
[11] Z. Otwinowski, W. Minor, DENZO/SCALEPACK, in: C.W.
Carter, Jr., R.M. Sweet (Eds.), Macromolecular Crystallography,
Part A, vol. 276, Academic Press, New York, pp. 307–326.
[12] A.M. Altamare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
M.C. Burla, G. Polidori, M. Gamalli, J. Appl. Crystallogr. 27
(1994) 435.
(c) C. Nguyen, R.J. Guajardo, P.K. Mascharak, Inorg. Chem. 35
(1996) 6273;
(d) R.J. Guajardo, S.E. Hudson, S.J. Brown, P.K. Mascharak, J.
Am. Chem. Soc. 115 (1993) 7971.
[4] Y. Yang, F. Diederich, J.S. Valentine, J. Am. Chem. Soc. 113
(1991) 7195.
[5] (a) C.P. Horwitz, D.R. Fooksman, L.D. Vuocolo, S.W. Gordon-
Wylie, N.J. Cox, T.J. Collins, J. Am. Chem. Soc. 120 (1998) 4867;
(b) S.S. Gupta, M. Stadler, C.A. Noser, A. Ghosh, B. Steinhoff,
D. Lenoir, C.P. Horwitz, K. Schramm, T.J. Collins, Science 296
(2002) 326.
[13] G.M. Sheldrick, SHELXTL Version 5.0, Siemens Analytical X-ray
Instruments Inc., Madison, 1995.
[14] A.L. Spek, Acta Crystallogr. A46 (1990) C34.
[15] STOE, X-RED, Data Reduction for STADI4 and IPDS, Revision
1.08. Stoe and Cie, Darmstadt, Germany.
€
[6] S.K. Dutta, U. Beckmann, E. Bill, T. Weyhermuller, K. Wieg-
hardt, Inorg. Chem. 39 (2000) 3355.
[16] G.M. Sheldrick, SHELXL-97 Program for Crystal Structure
€
Refinement, University of Gottingen, Germany, 1997.
[17] G.M. Sheldrick, SHELXS-97 Program for Crystal Structure
[7] (a) A.K Patra, M. Ray, R. Mukherjee, Inorg. Chem. 39 (2000)
652;
€
Solution, University of Gottingen, Germany, 1997.
(b) A.K. Patra, R. Mukherjee, Polyhedron 18 (1999) 1317;
(c) M. Ray, R. Mukherjee, J.P. Richardson, R.M. Buchanan, J.
Chem. Soc., Dalton Trans. (1993) 2451.
[18] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[19] S. Zhan, Q. Meng, X. You, Polyhedron (1996) 2655.
[20] T.L. Lu, H.Y. Kao, D.I. Wu, K.C. Kong, C.H. Cheng, Acta
Crystallogr. C44 (1988) 1184.
[8] (a) J.C. Chambron, K.J. Hiratani, Chem. Soc., Dalton Trans.
(1991) 1483;
[21] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, fifth ed., Wiley, New York, 1997, Part
B, p. 105.
(b) T. Hirose, K. Hiratani, K. Kasuga, K. Saito, T. Koike, E.
Kimura, Y. Nagawa, H. Nakanishi, J. Chem. Soc., Dalton Trans.
(1992) 2679.
[22] M. Giraudet, B. Meunier, Tetrahedron Lett. 28 (1987) 2955.